Aspects of the present disclosure relate generally to wireless communications, and more particularly, to techniques for managing radio link failure (RLF) recovery for a user equipment (UE) connected to both a wireless wide area network (WWAN) and a Wireless Local Area Network (WLAN).
Wireless communication networks are widely deployed to provide various communication services such as voice, video, packet data, messaging, broadcast, etc. These wireless networks may be multiple-access networks capable of supporting multiple users by sharing the available network resources. Examples of such multiple-access networks include Code Division Multiple Access (CDMA) networks, Time Division Multiple Access (TDMA) networks, Frequency Division Multiple Access (FDMA) networks, Orthogonal FDMA (OFDMA) networks, and Single-Carrier FDMA (SC-FDMA) networks.
A wireless communication network may include a number of enhanced Node Bs (also referred to as eNodeBs or eNBs) that can support communication for a number of user equipments (UEs). A UE may communicate with an eNodeB via the downlink and uplink. The downlink (or forward link) refers to the communication link from the eNodeB to the UE, and the uplink (or reverse link) refers to the communication link from the UE to the eNodeB.
A key enhancement being introduced into the current 3rd Generation Partnership Project (3GPP) family of specifications (or standards) is dual connectivity for a UE with both a wireless wide area network (WWAN) (e.g., Long Term Evolution (LTE) or Universal Mobile Telecommunications System (UMTS)) and a wireless local area network (WLAN) (e.g., Wi-Fi). As such, a UE may be in communication with both an eNodeB and a WLAN access point (AP).
Given this dual connectivity, WWAN congestion can be alleviated by sending data traffic over the WLAN (e.g., offloading from LTE to WLAN) to improve overall system capacity. To this end, Radio Access Network (RAN)-based traffic aggregation between the cellular RAN and the WLAN is being introduced into the 3GPP family of standards. In this approach, Radio Resource Controller (RRC) commands signaled by the cellular RAN are used to offload traffic to the WLAN (e.g., when the cellular RAN is congested) or to steer it back (e.g., fallback) to the cellular RAN (e.g., if the WLAN radio conditions become poor and/or cellular congestion has abated).
When a radio frequency (RF) environment between the UE and a WWAN access node (e.g., eNodeB in LTE) becomes poor, the UE may enter Radio Link Failure (RLF). Generally, when LTE RLF occurs, the RRC connection for a UE is suspended until the UE recovers from RLF (e.g., completes RLF recovery processing). As such, some LTE Signaling Radio Bearers (e.g., SRB 1) are not available during this time. Furthermore, all data traffic, which also may be referred to as data flows (e.g., data radio bearers (DRB) for LTE) for the WWAN are suspended and WLAN reporting entries in RRC are cleared by the UE. For a UE that is in communication with both an eNodeB and a WLAN access point, although the operations between LTE and WLAN are independent, the LTE RLF can have a serious impact on cellular RAN-based WLAN interworking since (1) any WLAN offloading and/or fallback decisions are performed by the cellular RAN, and (2) WLAN measurement reporting from the UE is performed via RRC messages.
Currently under the 3GPP family of standards, LTE RLF processing includes three aspects: (a) RLF detection, (b) Cell Reselection, and (c) RRC Connection Reestablishment. None of these aspects, however, include guidance on how to handle WLAN data flows during recovery from LTE RLF. In view of the foregoing, it may be understood that there may be significant problems and shortcomings associated with current RLF processing when a UE is interworking between LTE and WLAN.
As such, improvements in managing RLF recovery for a UE connected to both cellular and WLAN networks are desired.